Fluorescent folic acid-chitosan/carbon dot for pH-responsive drug delivery and bioimaging.

Nowadays, one of the most important reasons of death in the world is cancer. With the development of nanotechnology, advanced methods for treatment of cancer have introduced. In this work, the fluorescent carbon dots (CDs) were prepared from chitosan as the second abundant polysaccharide present in the nature. The surface of CDs was modified with chitosan (CDs/CS) and then the amino groups of chitosan were conjugated with activated folic acid (CDs/CS-FA) for controlled delivery of doxorubicin (DOX) as anticancer drug against HeLa cancer cells. The DOX loading efficiency of fluorescent CDs/CS-FA was high and nearly 60 %. Due to pH sensitive swelling/deswelling of CS, the percentage of cumulative DOX release could reach 90 % at cancer tissue (pH of 5.0) and 52 % at normal tissue (pH of 7.4) within 30 h. The cytotoxicity study revealed that the synthesized CDs were highly compatible on HeLa cells with cell viability 97-88 %. Cellular imaging shows that the entry of CDs/CS-FA to HeLa cells causes a green fluorescence, while the CDs/CS without FA have a negligible fluorescence. These results are due to the important role of FA in cell internalization. Thus, the CDs/CS-FA nanocarrier is suitable candidate for controlled pH sensitive drug delivery and cellular imaging.